Apparatus for producing fine continuous filaments



Dec. 27, 1966 G. R. MACHLAN ETAL 3 5 APPARATUS FOR PRODUCING FINECONTINUOUS FILAMENTS Filed April 1, 1965 5 Sheets-Sheet 1 650F615 RMACHL/I/V, CHARL 5 1, Mam/M5 &

HELL/W07 5L ASE/ INVENTORS Dec. 27, 1966 G. R. MACHLAN ETAL 3,294,503

APPARATUS FOR PRODUCING FINE CONTINUOUS FILAMENTS Filed April 1, 1963 5Sheets-Sheet 2 HELLMUT 6145/9? INVENTORS A TTORNE VS 1966 e. R. MACHLANETAL $294,503

APPARATUS FOR PRODUCING FINE CONTINUOUS FILAMENTS 5 Sheets-Sheet 3 FiledApril 1, 1963 GEO/P65 R MAO-MAN, CHARLES L. McK/N/m & HELLMUT 6LA5AINVENTORS United States Patent 3,294,503 APPARATUS lFtDR PRQDUQHNG FENECQNTKNUUUS FELAMENTS George R. Maehian, Newark, and (Zharles L.McKinnis,

Granville, Uhio, and Helhnut I. Glaser, Anderson, S.C,,

assignors to Owens-Corning Fiberglas Qorporation, a

corporation of Delaware Filed Apr. 1, 1963, Ser. No. 269,510 5 flaims.(Cl. 651l) The present invention relates to fine continuous filamentsformed of heat-softenable mineral material, such as glass, and to amethod and apparatus for forming extremely fine filaments rendering theproduction of such filaments economical on a commercial scale.

Strands of continuous filaments formed of glass have been producedcommercially and utilized in forming fabrics and such fabrics have theadvantage of good strength characteristics and stability. Commercialstrands of continuous filaments that have been produced commerciallyhave been of sizes greater than an average filament diameter of twentyhundred thousandths of an inch. It has been found that while suchfilaments have high strength characteristics, greater flexibility offiner filaments is desirable in fine fabrics particularly as suchfabrics must be capable of withstanding folding.

Fabrics heretofore made of yarns of glass filaments, while exhibitinggood Wear characteristics, have not had good resistance to abrasion andexhibited poor fiexure characteristics. It has been found that bysubstantially reducing the size or diameter of the continuous filamentsthat the strands of these very fine filaments woven or fashioned intofabric provide a fabric having substantially higher tensile strength andimproved folding, fiexure and abrasion resistant characteristics. Theyexhibit improved drape and a more softer luxurious hand or appearancewith greatly increased resistance to wear and hence a much longer life.

While it has been possible to attentuate glass into extremely finefilaments, it has not heretofore been economical to produce extremelyfine filaments on a commercial scale by reason of numerous difficultiesin effecting start-up upon break-outs of one or more filaments and thetendency of the glass to flood across the space between adjacent glassstreams.

The present invention embraces a method of forming and processingstreams of heat-softened mineral material to form continuous extremelyfine filaments collected in strand formation whereby the commercialproduction of yarns of extremely fine continuous filaments may beeffected.

An object of the invention resides in a method of producing extremelyfine filaments of glass by attenuation of streams of glass involvingdelivery orifices of special character and environment whereby thestart-up time or time required to reinitiate attenuation after filamentbreakouts is greatly reduced over prior methods.

Another object of the invention resides in a method of flowing streamsof heat-softened glass through orifices in a manner reducing thetendency of the glass to flood and facilitating the employment of acomparatively large number of stream feeding orifices whereby extremelyfine continuous filaments are attenuated from the streams to form astrand comprising a large number of extremely fine filaments which maybe produced economically and on a commercial scale.

Another object of the invention is the provision of an arrangement forheat-conditioning glass or other mineral material for the production offine filaments from streams of the material wherein the pieces ofmaterial or batch are reduced to a fiowable state under conditionspromoting a uniform throughput of the glass through the Patented Dec.27, 1%66 delivery orifices with a minimum of temperature variation andthereby minimize break-outs and interruption of attenuation of thestreams to filaments.

Another object of the invention is the provision of a method ofheat-conditioning the glass in a glass melter region providing acomparatively long residence time for the glass in the heatedenvironment sufiicient to promote the movement of the molten glass inlaminar planes, the glass moving downwardly substantially uniformlythrough the feeder or bushing section to the delivery orifice or tipsection whereby channeling of the glass or the tendency of the glass tomigrate through adjacent laminae is substantially eliminated.

Another object of the invention is the provision of an arrangement forheat-conditioning glass or other filamentforming mineral material in amelter and feeder construction to attain a substantially uniformtemperature glass to promote a uniform throughput with a minimum oftemperature variation reduced to a tolerance fact-or satisfactory forthe attenuation of fine filaments with a minimum of break-outs.

Another object of the invention is the provision of the method ofprocessing glass or other filament-forming mineral material by meteringthe input of glass or filamentforming mineral rnaterial into a melterregion in a manner whereby temperature variations set up by reason ofthe introduction of pieces of glass or batch into the melt are reducedto a minimum well Within a temperature tolerance satisfactory for theattenuation of extremely fine filaments.

Another object of the invention resides in the provision of streamfeeder tips and their orientation on a feeder or bushing tip sectionwhereby the time required to form a bead of molten glass at a tip andthe time within which such bead drops from the initiation of itsformation are reduced and thereby reducing the start-up time of filamentattenuation, rendering the process commercially economical for theproduction of extremely fine continuous filaments.

Another object of the invention resides in the provision of a novelfeeder tip and orifice construction for the delivery of molten glasswherein the tip face and other dimensional characteristics of the tipare proportioned to reduce the bead formation and bead drop time to aminimum and to reduce the lateral dimension of a head to enablepositioning a plurality of tips in close relation with a minimumliability of flooding to enable the simultaneous attenuation of acomparatively large number of extremely .fine filaments gathered into asingle strand and reducing the liability of break-outs to fostercontinuous attenuation.

Another object of the invention resides in the provision of a feederhaving a large number of orificed tips having particular dimensionalcharacteristics and the tips oriented in a manner and the molten glassmaintained at a temperature which accelerates the formation of a bead incase of break-out of the filament formed from the stream and reducingthe bead weight to promote a more rapid bead drop time to facilitatefaster restarts of the winding operation in a minimum of time.

Further objects and advantages are within the scope of this inventionsuch as relate to the arrangement, oper ation and function of therelated elements of the structure, to various details of constructionand to combinations of parts, elements per se, and to economies ofmanufacture and numerous other features as will be apparent from aconsideration of the specification and drawing of a form of theinvention, which may be preferred, in which:

FIGURE 1 is a semi-schematic elevational view of an arrangementembodying the invention and illustrating a method of processing andconditioning glass for attenuation of fine continuous filamentstherefrom;

FIGURE 2 is a vertical sectional view of the glass heating andconditioning apparatus of the invention;

FIGURE 3 is a sectional view taken substantially on the line 3-3 ofFIGURE 2;

FIGURE 4 is a bottom plan view of a portion of the tip section of astream feeder, and

FIGURE 5 is an enlarged fragmentary detail sectional view illustratingthe dimensional characteristics and orientation of the orificed tips ona stream feeder.

While the method and apparatus of the invention have particular utilityin heat-conditioning and processing glass for forming extremely finetextile filaments, it is to be understood that the method and apparatusof the invention may be utilized for conditioning and processing othermineral materials.

Referring to the drawings in detail and initially to FIG- URE 1, a formof the apparatus of the invention is illustrated which is especiallyadaptable for the formation of extremely fine continuous filaments ofglass for forming textile strands, threads or yarns. The arrangement isinclusive of a melter and feeder construction or unit forheat-conditioning glass which is flowed through orificed projectionsprovided on the floor of the feeder tip section as fine streams whichare attenuated into fine continuous filaments 12.

As shown in FIGURE 1, the continuous filaments 12 are attenuated bymechanical attenuation and, in the arrangement illustrated, areconverged to form a multi-filament strand 14 through the medium of agathering device or shoe 16, the strand 14 being wound upon a collectoror collecting surface in the form of a tubular sleeve 18 mounted upon amandrel 20 driven by suitable motive means (not shown) contained in awinding machine housing 22 of conventional construction. During windingof the strand 14 upon the collector 18, the strand is traversedlengthwise of the collector 18 to build up a strand package ofsuperposed layers of the strand, a traverse means 24 being engaged withthe strand and arranged to effect oscillation of the strand in order toeffect a crossing of successive convolutions of strand 0n the collectorto prevent adjacent convolutions of strand from adhering together. Alubricant, size or other coating material may be applied to thefilaments by engaging them with a roll applicator 26 of conventionalcharacter.

The arrangement illustrated in FIGURE 1 is adapted to melt orheat-condition pieces of glass such as preformed glass marbles 29introduced into the melter component of the unit 10 through chute means30 from marble metering or feeding means associated with a marblesupply.

The pieces of glass or marbles are metered by means dependent uponminute variations in the level of molten glass or material in themelting regoin. The melter and feeder unit 10 and the means for meteringthe delivery of marbles or pieces of glass into the unit and the supplyhopper are supported by a frame structure 32.

As shown in FIGURE 1, a member 33 of the frame 32 supports a supplyhopper 36 in the lower region of which is disposed a metering means inthe form of a drum 41 mounted upon a shaft 42 driven by a motor 44through suitable gearing 45 or other transmission mechanism. In

the embodiment illustrated, the drum 41 is provided with two rows ofsockets or recesses 46 of a character to receive marbles of glass fromthe hopper 36 and, upon rotation of the drum, are metered or deliveredthrough the feed chutes 30 into the melter region 60 of the unit 10.

The upper wall 50 of the unit 10 is provided with a tubular member 52 inwhich is disposed a probe rod or electrode 53 connected with a controlmeans contained within a programmer, shown schematically at 56, arrangedto regulate or control the operation of the motor 44 to deliver themarbles from the recesses in the drum through the chutes 30 into themelter. Electric power supply for the programmer 56 is indicated at L1and L2.

Through the programmer 56, a circuit is established through the probe 53to the motor 44 for effecting rotation of the marble feed drum 41 tosubstantially continuously feed glass marbles from the recesses 46 inthe drum to the marble chutes 30,

The rate of rotation of the motor 44 and the feed drum 41 is controlledto slightly overfeed glass marbles into the melter 60, that is, at arate slightly greater than the throughput of glass discharged as streamsfrom the feeder when the level of glass is below or out of contact withthe probe 53.

The overfeeding of glass into the melter raises the level of the glassto a point where contact is made between the probe 53 and the glass inthe melter. When this occurs, the probe circuit, through the programmer56 is arranged to reduce the speed of the motor 44 to feed the marblesor pieces of glass into the melter through the chutes 30 at a lesserrate than the rate of throughput of the glass by way of the streams andthereby reduce the level of the glass in the melter.

Thus the probe 53 establishes an overfeed of glass marbles to the melter60 when the glass is out of contact with the probe. The probe 53establishes an underfeed of marbles or glass into the melter when theglass contacts the probe. Through this level control arrangement, asubstantially constant head of molten glass is maintained in the melterand feeder unit 10. The cover 50 is provided with a vent tube forventing gases or volatiles given off by the glass in the melter.

FIGURES 2 and 3 illustrate one form of melter-feeder unit or arrangementfor melting and heat-conditioning glass from which extremely finecontinuous filaments may be formed. The arrangement comprises asubstantially rectangular melter region defined by side walls 62, a topcover plate 50, and end walls 64, the side and end walls being joinedwith the horizontal cover plate 50 by angularly arranged connectingportions 66 and 68. The cover plate 50 is fashioned with couplingbushings 51 which are in registration with the chutes 30.

The feeder section or region 70 is fashioned with side walls 72 whichare joined with the side Walls of the melter section by angularlyarranged connecting portions or plates 74, as shown in FIGURE 4. The endwalls 64 are provided with extensions forming end walls of the narrowerfeeder section 70. A current conducting or heater screen 76, preferablyformed of an alloy of platinum and rhodium in the shape of an invertedV, is disposed lengthwise between the melter region 60 and the feeder orconditioning region 70 as particularly shown in FIGURE 3 and isfashioned of suitable mesh to prevent the entrance of any unmeltedfragments or pieces of glass entering the feeder section. The highesttemperature in the melt is beneath and adjacent the heating screen 76,Thus the melting occurs in the chamber 60 and the temperatureprogressively increases to the region just beneath the screen 76. Fromthis region downward, the temperature of the glass gradually decreasesin a manner to promote movement in laminar planes to effectively refineand render the glass homogeneous for attenuation.

Welded to each end of the melter-feeder unit 10 are terminals which areconnected by clamps 81 with suitable bus bars or current conductors 82which are connected by conductors 83, shown in FIGURE 1, with a sourceof electric current L3, L4 through a control unit 58 which provides themedia for melting the glass in the melter section and heat-conditioningthe glass in the feeder or conditioning section to the desired viscosityto obtain a required throughput through the orifices in a tip section ofthe feeder.

The current supply circuit to the terminals 80 is of low voltage andhigh amperage and is regulated by conventional means in the control unit58 for melting the glass and maintaining a proper temperature of theglass in the feeder section. Thermocouples (not shown) are disposed invarious regions of the feeder and melter sections for indicating to anoperator the temperature of the glass in the sections. The amount ofelectric current flow through the unit determines the rate of melting inthe melter and the temperature of the glass in the feeder section and iscontrolled by conventional means in the control unit 58 connected withheat responsive devices (not shown) positioned in the unit 10. It shouldbe noted that the melter section is of substantial depth and that thefeeder section is narrower than the melter section and is of substantialdepth in order to maintain a comparatively large amount of glass in themelter and feeder sections. By providing a substantial amount of glassin the unit It) a sumcient residence time is had for the glass in themelter and feeder to promote the heat-conditioning of the molten glassin laminar planes so that the molten glass in the feeder section at theregion of the delivery orifices is of uniform temperature andsubstantially homogeneous throughout so that the same amount ofthroughput is had through each of the orificed tips. The dimensional andflow characteristics of the melter and feeder construction should befashioned to provide for a residence time of about one and one-halfhours or more for the economical production of fine filaments. Therefractory 85 surround ing the melter 60 and conditioning region 70should be comparatively thick to stabilize the temperatures to promotelaminar flow. The conditioning region 70 should be relatively narrow inwidth in order to maintain temperature control at the central region asotherwise laminar flow will be impaired.

The receptacle providing the melter region and feeder region may befashioned of metals or alloys capable of withstanding the intense heatof the molten glass or other mineral material, and alloys of platinumand rhodium have been found to be generally satisfactory for thepurpose.

The floor of the feeder comprises a component or sec tion, usuallyreferred to as a tip section, which is formed with depending hollowprojections or tips providing passages or orifices through which flowsstreams of molten glass from the feeder. In the embodiment illustrated,the feeder or tip section 959 is of generally rectangular shape having ahorizontal planar floor portion d2 with which are joined upwardly andoutwardly converging walls or wall portions 94 terminating in flangeswhich are welded to outwardly extending flanges 98 formed on the sidewalls 72 of the feeder section '75.

The tip section $0 is preferably fashioned of an alloy of platinum andrhodium but may be fashioned of other suitable high temperatureresistant metals or alloys. The tip section 9% is formed with aplurality of depending projections 1%, usually referred to as tips, eachtip being formed with an orifice, channel or passage through which astream of molten glass is delivered from the feeder.

The number of orifices and hence the number of streams of glass flowingfrom the feeder determine the number of fine filaments as a continuousfilament is attenuated from each stream.

The projections 109 are arranged in transverse and lengthwise rows inthe manner illustrated in FIGURE 4, the spacing of the rows and thecharacter and dimensions of the projections and orifices or passagestherein being major factors in the economical production of extremelyfine continuous filaments. The geometry of the tip construction and thefactors affecting the production of continuous filaments will behereinafter described.

In order to promote flow from the tip section of streams of molten glassof uniform size and characteristics, the molten glass in the feedersection is maintained at a temperature above an attenuating rangeproviding a more liquid glass to be delivered through the orifices. As ahighly liquid glass is of too low viscosity for satisfactoryattenuation, an arrangement is provided adjacent the delivery region ofthe streams from the projections or tips 1% to condition and stabilizethe viscosity of the glass to facilitate attenuation.

As shown in FIGURES 1 through 4, there is disposed lengthwise of the tipsection a tubular manifold 164 having inlet and outlet tubes 105 and 1%for connection with a heat-absorbing or heat transfer medium, such asWater circulated or flowing through the manifold. Welded or otherwisejoined with the manifold in heat transferring relation therewith is aplurality of heat transferring fins or members 108.

In the embodiment illustrated, as particularly shown in FIGURE 5, a finor member 1&8 is disposed between each transverse row of projections ortips to absorb or withdraw heat from the streams of glass to increasethe viscosity of the glass of the streams to a satisfactory attenuatingtemperature or condition. While, in the embodiment illustrated, a fin ormember 100 is provided between each transverse row of projections, it isto be understood that, if desired, one fin may extend between alternaterows, but in such construction the projections between adjacent fins aredisposed in closer relation.

FIGURE 5 illustrates, on a greatly enlarged scale, a form of projectionor tip construction 100 typical of a character suitable for flowingstreams of glass for attenuation to extremely fine filaments. Filamentsformed by the method or process of the invention are in a size rangeunder eighteen hundred thousandths of an inch in diameter. For example,strands formed of continuous filaments having an average diameter offourteen hundred thousandths of an inch have been produced, and testshave been successful in producing filaments of less than eight hundredthousandths of an inch through the use of the method of the invention.

There are several factors which are found to be important in the methodof forming extremely fine continuous filaments within theabove-mentioned size range which bear upon the economical and commercialproduction of the fine filaments. Among the important characteristics isthe factor of the start up time after a breakout in initiating theformation of the continuous filaments.

Major conditions affecting start-up time are the weight of the head ofglass which forms upon break-out of a filament and the lapsed time offormation of the bead until it drops, that is, when the weight of thebead is sumcient to allow the bead to drop.

It is found that the bead drop time must be reduced to a minimum as thislapsed time determines the handling time or downtime in effecting arestart of filament attenuation. Thus, to render the processcommercially economical, the handling time, that is, the start-up timemust be reduced as low as possible as such wasted or downtime, ifexcessive, renders the process or method too costly for commercialadaptation.

We have found that the weight of the bead formed at the tip and itsperiod of formation, which determines the drop time, is dependent in alarge measure upon the dimensional characteristics of the orifices andconfiguration of the tip and the surface thereof from which the streamis discharged. FIGURE 5 illustrates an exemplary tip configuration of acharacter employed in the method and process of producing extremely finecontinuous filaments within the size range above-mentioned.

One characteristic of the tip configuration affecting the bead size anddrop time is the area of the face or edge of the tip or projection, thatis, the area of the annuiar region or marginal edge defining the exit oroutlet of the passage in the projection. This diameter is designated inFIGURE 5 at D6 and the annular face area is designated 112. We havefound that the marginal edge or wall at the outlet, designated D6 inFIGURE 5, should be made as thin as is practicable, preferably fivethousandths of an inch or less to minimize bead drop time and handlingtime. While the marginal edge or wall may be made of greater thicknessin the order of ten thousandths of an inch and produce fine filaments,the increased wall thickness increases the bead drop time and hencetends to increase the start-up or handling time after interruptions dueto breakouts.

By reducing the area of the marginal edge or annular tip face, the beadweight and drop time are reduced, which factors directly affect thehandling or restarting time.

The spacing between adjacent tips designated S is important in tworespects, first, the spacing should be reduced to a minimum tofacilitate the use of a large number of tips on one feeder section toform a large number of fine filaments and, second, the distance betweenadjacent tips must be sufficient to prevent intercontact betweenadjacent beads formed on the tips in order to minimize the tendency toflooding, that is, the tendency for the molten glass to migrate alongthe exterior surfaces of the projections or tips.

Other factors affecting bead weight and drop time are the size of theorifice, the length of the orifice, the rate of throughput, and thetemperature and hence viscosity of the glass in the feeder and in theorifice, and at the region of the formation of the bead adhering to theannular face of a tip through interfacial tension. It is found that thehigher the temperature of glass and correspondingly lesser viscosity,the bead weight may be reduced.

It is desirable that the temperature of the glass in the restrictedpassage or orifice channel 114 be comparatively high so that the glassis at a low viscosity to promote the delivery of uniform streams fromthe orificed tips 100.

The size of the orifice channel 114 and its length affect the throughputof glass. The restricted orifice channel 114 is an important factor inmetering or regulating the flow rate or throughput of glass and, as thewalls of the orifice channel offer resistance to fiow, an increase inthe length of the orifice channel reduces the throughput.

With particular reference to FIGURE 5, in the form of tip illustratedtherein, a counterbore 116 is provided of larger diameter than themetering channel or orifice 114, the difference between the diameter ofthe counterbore 116 and the diameter of the tip face 112 determining thearea of the annular tip surface.

The bead formation and drop time is a function of the throughput, thepulling speed for forming continuous filaments, within the size rangementioned above, is upwards of eight thousand or more linear feet perminute. In addition to the throughput, the area of the tip edge or face112 of the tip and the viscosity at which the glass is attenuated tofilaments are factors which contribute to the tension or stress set upin the filaments due to the rapid attenuation of the streams.

Another factor bearing upon the throughput is the depth or head of glassin the feeder-melter unit or receptacle and, furthermore, if pressure isexerted upon the glass in the melter-feeder unit, other factorsremaining unchanged, the bead forming and drop time is lessened, furtherreducing the handling or restarting time. In the embodiment illustrated,the head of glass is maintained at the approximate level illustrated inFIGURES 2 and 3 providing a substantially constant head of glass.

If desired, however, the melting and feeder unit may be placed underpressure by a connection with a suitable gas under pressure, gating thechutes 30 and closing the vent 55 so as to maintain pressure on theglass in the unit. However, at the present time, it appears that theincreased cost of pressurizing the receptacle would be greater than thesavings effected through reduced handling time with a pressurized unit.

While the dimensions of or geometry of the tips or projections may bevaried, the following are approximate ranges for various dimensions ofthe tip and orifice construction which have been found satisfactory inthe production of fine filaments in the filament size rangeabovementioned. With particular reference to FIGURE 5, the flow meteringor delivery orifice channel 114 may be of a diameter D1 up to .045 of aninch and preferably less, with or without the counterbore.

The counterbore is usually employed in order to reduce o the wallthickness at the region of the outlet or orifice in order to minimizethe area of the tip face or edge 112. Hence the counterbore diameterindicated at D2 may be in the range from the size of the restriction D1up to a diameter of approximately .060 of an inch. If the counterbore116 is not used, and the orifice channel or passage 114 continued to thetip as indicated in broken lines at 118 and being of a uniform diameter,the diameter D1 or size of the channel 114 should be increased tocompensate for the resistance of the added length of the orifice channel114 to obtain the same throughput.

With a metering orifice channel 114 in the size range above specified,the diameter D4 of the tip face would be of a dimension to provide adesired area for the annular face 112, preferably of small area. Thediameter D1 is dependent upon the diameter and length of the counterboreD2. If the counterbore is not used, and the diameter of the orificechannel 114 is continued to the tip face 112, the diameter D4 may bereduced to a dimension to provide a minimum practical thickness for thewall adjacent the tip face. The thickness LW of the plate portion of thetip section is approximately sixty thousandths of an inch.

The over-all length LT from the planar interior surface 120 of thefeeder section 90 is important in that the length bears upon thetendency of the glass to flood over the lower surface of the tipsection. With the abovementioned range of dimensions for the orificechannel 114, the counterbore D2 and the diameter of the tip face D4, itis found that the projection from the lower surface of the feedersection 90 may be of a length up to approximately one hundred eightythousandths for satisfactory operation but is preferably of a lesserlength to a minimum at which excessive flooding may occur. It has beenfound that if the over-all length LT of a tip is shortened, a reductionin the diameter of the orifice channel 114 should be made in order tomaintain the same resistance to glass flow.

Another factor particularly affecting the viscosity of the glass in theorifice channel 114 is the angularity of the tapered wall regions 124defining the tip or projection 100. The projection being generally ofthe shape shown in FIGURE 5, it Will be noted that at the regionadjacent the orifice channel 114, there is a substantial thickness ofmetal of the tip 100. Due to the thickness of the metal of the tip orprojection at this region, the glass will be at its maximum temperaturein the orifice channel and hence at its lowest viscosity to promotesatisfactory fiowability through the orifice channel 114.

From this region downwardly the glass loses heat more rapidly throughradiation and convection so that the glass at the region of the tipsurface 112 is more viscous than the glass in the metering or orificechannel 114.

When a break-out occurs, a bead of glass begins to form under theinfluence of continued fiowof glass through the orifice passage orchannel 114 and, by reason of the surface tension and afiinity of theglass to cling to other bodies, the bead 130 is built up in size bygravity flow. As the bead weight increases, the bead moves downwardly toa broken line position, as shown at 130', and the region of the glassadhering the bead to the tip surface begins to neck in as shown inbroken lines at 132.

When the weight of the bead exceeds the force holding the bead insuspension from the tip face 112, the bead drops and, during its descentby gravity, attenuates a continuous thread or monofilament from theglass adhering to the tip face 112. This trailing monofilament enablesthe operator to effect a restarting by gathering this bead-attenuatedmonofilament with the other filaments and initiate start-up by windingthe filaments on the rotating collector sleeve 18 and restore high speedproduction attenuation of the streams into fine filaments.

From the foregoing it will be apparent that the bead formation time,that is, the time from its inception after 9 a break-out until the beaddrops by gravity to form a bead-attenuated monofilament, determines thelapsed or down time until the attenuating process can be restarted bythe operator in the manner above-described. Thus, one of the importantfactors of the invention resides in the correlation of the factorsabove-mentioned in a manner to reduce, insofar as possible, the beadforming or bead drop time as this factor determines the handling time ininitiating start-up, and reduction of this time renders possible thecommercial use of the process on an economical scale. An importantfactor in reducing the bead forming and drop time is the area of theannular edge or tip face 112. The area of this face should be reduced toa minimum practicable for satisfactory attenuation. Another reason formaintaining the tip face diameter D4 as small as possible is to enablethe use of a greater number of tips or projections on a tip section areain order to form a strand or yarn having a large number of extremelyfine filaments or ends.

Heretofore continuous filaments of a diameter of twenty hundredthousandths of an inch and filaments of larger sizes have been producedcommercially. In applying the methods that have heretofore been used inproducing strands of filaments of twenty hundred thousandths of an inchin diameter or larger to the formation of extremely fine filaments inthe order of fourteen hundred thousandths of .an inch, the bead droptime has been found to be at least six minutes or more in duration andhence, when a breakout occurred, it required a minimum of twenty minutesor more to restart the attenuating operation.

In the process of our invention the bead formation and drop time hasbeen reduced to about one minute and the handling time thereby reducedto about two minutes. This substantial decreasein handling time makespossible the commercial production of the extremely fine filaments lessthan eighteen hundred thousandths of an inch in diameter.

While the tip section illustrated in the drawings is of rectangularshape, it is to be understood that a tip section of other shape, or agroup of tip sections arranged in close relation, may be employed forcarrying out the method of the invention.

When fine filaments of the size less than eighteen hundred thousandthsof an inch in diameter are combined in a strand or yarn, a textilematerial is provided which has a very high degree of flexibility and ismuch stronger per unit of cross-sectional area than glass fiber yarnsheretofore produced. We attribute the improved flexibility and strengthcharacteristics to the fineness of the filaments. It has been found byactual tests that the mechanical properties of a fabric formed with thenew fine filament yarns are a high burst strength, improved flexibility,higher resistance to abrasion, higher breaking strength and improvedwashability, improved wearability and better folding resistance. It isknown that glass yarns and textile materials of glass fibers orfilaments tend to irritate the skin.

It is found that the strands, yarns or fabrics formed therefromembodying the new fine filaments of the in vention materially reducesthe irritation factor. It has further been found that the yarns orthreads formed from the new fine filaments are of such high flexibilitythat they may be readily processed on conventional knitting and weavingmachines.

The uniformity or homogeneous character of glass utilized in forming thefine filaments is a contributing factor to the success of the process.Uniformity of the melt and more especially its laminar characteristicsare dependent in a large measure upon the residence time of the glass inthe melter and feeder unit in the heat-conditioning phase of theprocess. Hence it is essential to maintain a substantial quantity ofmolten glass in the melter chamber 60, approximately at the levelillustrated in FIGURES 2 and 3. While a particular glass compositionemployed in the process may have some effect on the formation and droptime of a bead, it has been found that filament-forming glasscompositions of conventional character may be employed although certainpercentages of the ingredients or components in the composition may bemodified or varied to change or modify the viscosity characteristics ina minor degree but it is not essential to successful attenuation of thefine filaments to employ a glass of special specifications.

The use of a counterbore D2 is to reduce the wall thickness of the tipor projection at the outlet region in order to minimize the area of theannular tip face 112 to facilitate the use of a substantial amount ofmetal surrounding the metering restriction or channel 114 to minimizethe thermal losses at the region of the tip or projection defining thechannel. It is therefore desirable to make the counterbore D2, where itis used, of a short length so as not to impair the thermal environmentat the tips in order to maintain uniform throughput.

In reference to head drop time as affecting the duration of start-up orhandling time, it is to be understood that the bead drop time of anindividual glass stream should be as of short duration as possible. Inthe use of several hundred tips on a feeder, the individual bead droptime is not fully determinate of the start-up or handling time for theseveral hundred filaments.

For example, tests have shown that with a feeder equipped with 408outlets or orifices and a bead drop time from a single orifice of sixminutes, the handling or start-up time, that is, the time required foran operator to gather all of the 408 filaments into a strand andinitiate winding of the strand upon a winding collet, consumesapproximately twenty minutes or more. Hence, the handling or start-uptime is of greater duration than the bead drop time for the reason thatrepeated starts may be necessary due to breakage of one or more of thefine filaments during the gathering of the filaments into a strand andits initial Winding on the winding collet.

With our invention, the bead drop time has been reduced to approximatelyone minute, and for a feeder having 408 orifices, the handling orstart-up time is only about two minutes. If a greater number of orificesor outlets is provided on a feeder, the average handling or start-uptime is increased due to the greater probability of difficulties ingathering the larger number of filaments into a strand and initiatingwinding of the strand. Hence the handling time is a function of thenumber of streams and hence the number of filaments to be embodied inthe strand.

In the use of our invention, Where the bead drop time is reduced toapproximately one minute, the average handling or start-up time for agroup of filaments from a feeder having 408 orifices is reduced toapproximately two minutes because of the reduced tendency for breakoutof filaments by reason of the several factors such as the high degree ofhomogeneity of the glass, the thermal environment and the geometry ofthe tips including the reduction in the area of the tip faces or edges112.

While fine filaments may be produced where the thick ness of the wall ofthe tip adjacent the tip face is greater than five thousandths of aninch, the increase in area of the tip face promotes an increase in thebead drop time and a proportionately greater increase in the start-up orhandling time. The frequency of occurrence of breakouts and hence thenumber of start-ups have a direct bearing upon the cost of producingfine filaments so as to render the process commercially economical. Itis therefore a general principle of the invention to correlate thevarious factors and the geometry of the tip section or feeder section topromote a minimum of head drop time and hence reduce the handling orstart-up time to render the process commercially feasible.

While the arrangement shown in FIGURES'I through 3 is particularlyadapted for processing preformed marbles or spheres of glass int-oextremely fine glass filaments, it

is to be understood that the process may be utilized with the forehearthof a melting furnace in which arrangement molten glass would bedelivered to the feeder tip section with a proper quantity in a feedersection providing for sumcient residence time for the glass to properlyheat-condition the glass for attenuation into fine filaments.

It is apparent that, within the scope of the invention, modificationsand different arrangements may be made other than as herein disclosed,and the present disclosure is illustrative merely, the inventioncomprehending all variations thereof.

We claim:

1. A stream feeder for flowing streams of molten glass from a supplycomprising a planar feeder section formed of high temperature resistantmetallic material, a plurality of spaced metallic tips depending fromthe planar section, each of said tips being formed with a meteringpassage of circular cross-section and a tip face of annularconfiguration, the diameter of the tip face being not more than twentythousandths of an inch greater than the diameter of the outlet of themetering passage.

2. A stream feeder for flowing streams of molten glass from a supplycomprising a planar feeder section formed of high temperature resistantmaterial, a plurality of spaced tips integral with and depending fromthe planar section, each of said tips being formed with a passage ofcircular cross-section and an annular tip face of comparatively smallarea, the diameter of the tip face being not more than seventythousandths of an inch, adjacent tips being spaced apart a sufficientdistance whereby beads of molten glass suspended from the tips aremaintained out of contact and thereby avoid flooding of the feedersection.

3. Apparatus for forming continuous fine filaments of heat-softenedmineral material including, in combination, a stream feeder arranged tocontain a supply of the heat-softened material in a flowable condition,said stream feeder having a floor formed with a plurality of dependingprojections of uniform length, each of said projections being formedwith a restricted passage having a discharge outlet not exceeding sixtythousandths of an inch in diameter, the extremity of each projectionbeing of a diameter not exceeding seventy thousandths of an inch, saidprojections being spaced whereby beads of the softened mineral materialsuspended from the projections are in close relation but out of contactto prevent flooding.

4. A stream feeder for flowing streams of molten glass from a supplycomprising a planar feeder section formed of high temperature resistantmaterial, a plurality of spaced tips integral with and depending fromthe planar section, each of said tips being formed with a passage, themarginal edge defining the outlet of the passage being of a thicknessnot greater than five thousandths of an inch.

5. Apparatus for forming continuous fine filaments of heat-softenedmineral material including, in combination, a stream feeder arranged tocontain a supply of the heat-softened material in a flowable condition,said stream feeder having a floor formed with a plurality of dependingprojections of uniform length, each of said projections being formedwith a restricted passage having a discharge outlet not exceeding sixtythousandths of an inch in diameter, the thickness of the wall of theprojection at the discharge outlet being not more than ten thousandthsof an inch.

References Cited by the Examiner UNITED STATES PATENTS 1,427,014 8/1922Von Pazsiczky l1 1,796,571 3/1931 Mathieu 18-8 2,846,157 8/1958 Stephenset a1 651 X 2,947,027 8/ 1960 Slayter 65-4 2,996,758 8/1961 McFadden65--1l 3,066,504 12/1962 Hartwig et a1. 65-l 3,192,023 6/1965 Stalego65l FOREIGN PATENTS 763,160 12/1956 Great Britain.

DONALL H. SYLVESTER, Primary Examiner.

C. VAN HORN, R. LINDSAY, Assistant Examiners.

4. A STREAM FEEDER FOR FLOWING STREAMS OF MOLTEN GLASS FROM A SUPPLYCOMPRISING A PLANAR FEEDER SECTION FORMED OF HIGH TEMPERATURE RESISTANTMATERIAL, A PLURALITY OF SPACED TIPS INTEGRAL WITH AND DEPENDING FROMTHE PLANAR SECTION, EACH OF SAID TIPS BEING FORMED WITH A PASSAGE, THEMARGINAL EDGE DEFINING THE OUTLET OF THE PASSAGE BEING OF A THICKNESSNOT GREATER THAN FIVE THOUSANDTHS OF AN INCH.